Clubtooth lever escapement

ABSTRACT

CLUBTOOTH LEVER ESCAPEMENT WITH HIGH TRANSMISSION EFFICIENCY HAVING AN ESCAPE WHEEL AND AN ANCHOR AND SATISFYING AT LEAST ONE OF 1.0&gt;LG/LAI$0.85 AND 1.0&gt;G/LAD$0.85. WHERE LG IS THE LENGTH OF THE IMPULSE FACE OF THE ESCAPE WHEEL TOOTH, LAI IS THE LENGTH OF THE IMPULSE FACE OF THE ENTRY PALLET JEWEL OF THE ANCHOR AND LAD IS THE LENGTH OF THE IMPULSE FACE OF THE EXIT PALLET JEWEL OF THE ANCHOR.

Nov. 30, 1.71 KENJI ABE CLUBTOOTH LEVER ESCAPEMEN'I 3 Sheets-Sheet 1Filed April 6, 1970 F/GJ FIG.2

Nov. 30, 1971 KENJI ABE CLUBTOOTH LEVER ESCAPEMENT 3 Sheets-Sheet 2Filed April 6, 1970 New. 30, 1971 KENJI ABE CLUBTOOTH LEVER ESCAPEMENT 3Sheets-Sheet 5 Filed April 6, 1970 T MN N 1 m M we N S M E Tm MM 5 C REP L woatfitwm N m United States Patent O 3,623,316 CLUBTOOTH LEVERESCAPEMENT Kenji Abe, Suwa-shi, Japan, assignor to Kabushiki Kaisha SuwaSeikosha, Tokyo, Japan Filed Apr. 6, 1970, Ser. No. 25,717 Claimspriority, application Japan, Apr. 16, 1969, 44/28,972 Int. Cl. G04b15/00 US. Cl. 58-116 3 Claims ABSTRACT OF THE DISCLOSURE Clubtooth leverescapement with high transmission efliciency having an escape wheel andan anchor and satisfying at least one of 1.0 L 120.85 and 1.0 L /L20.85, where L is the length of the impulse face of the escape wheeltooth, L is the length of the impulse face of the entry pallet jewel ofthe anchor and L is the length of the impulse face of the exit palletjewel of the anchor.

SUMMARY OF THE INVENTION The present invention relates toan improvedclubtooth lever escapement for a timepiece, and more particularly to thetransmission efficiency of the escapement. The length of the respectiveimpulse faces of the escape wheel tooth, the entry pallet jewel and exitpallet jewel are determined in accordance with a fixed relationship toincrease the transmission efficiency of the whole escapement.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of a conventionalclubtooth lever escapement;

FIG. 2 shows the operating relationship between the driving part(hereinafter referred to as an escape wheel portion) and the driven part(hereinafter referred to as an anchor portion) when they rotate in onedirection;

FIGS. 3 and 4 show the operating relationship between an escape wheeltooth and an entry pallet jewel;

FIG. 5 shows the operating relationship between an escape wheel portionand an anchor portion when the latter rotates in the opposite direction;

FIG. 6 is a graph showing the relationship between the 'mainspringtorque and the amplitude of the balance in a conventional escapement andalso in an escapement according to the present invention; and

FIG. 7 is a graph showing the relationship between the frequency and thetransmission efiiciency in a conventional escapement and also in anescapement according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a clubtooth leverescapement is composed of an escape wheel 1, an anchor 2 and a rollertable 3 of a balance. The roller table 3 is coaxially mounted on abalance staflf 13. When the roller table 3 rotates in the direction ofthe arrow 16 with the rotation of the balance, a roller jewel 12 strikesagainst a horn 11 of the anchor. This permits an entry pallet jewel 7 toleave its lock face 8. As the escape wheel 1 rotates in the direction ofthe arrow 14, the anchor 2 receives rotation torque in the direction ofthe arrow 15 and transmits the energy through the horn 11 of the anchorand the roller jewel 12 to the balance. An exit pallet jewel 7 thenlocks an escape wheel tooth against rotation and at the same time theanchor 2 is pressed against a banking pin '10. While the balance rotatesin the opposite direction to the arrow 1l6, said exit pallet jewel takesthe same actions as said entry pallet jewel.

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The escape wheel tooth is provided with a lock face 5 and an impulseface 6. The entry pallet jewel 7 of the anchor is provided with a lockface 8 and an impulse face 9, while the exit pallet jewel 7 is providedwith a lock face 8 and an impulse 9. Therefore, the energy transmissionfrom the escape wheel 7 to the anchor 2 is accomplished at the impulsefaces thereof.

Generally the following matters have been studied in order to improvethe transmission efficiency of the clubtooth lever escapement.

(l) The friction caused in the impulse face 6 of the escape wheel toothand in the impulse face 9 (9) of the anchor pallet jewel 7 (7') has beenreduced as much as possible by the following treatment. Each face wassufficiently polished, and the lubricant supplied thereto. Materialshaving a low frictional coefficient such as ruby were applied to thepallet jewels, and contact surfaces were made smaller.

(2) The escapement was made small and thin to the greatest extentpossible from the viewpoint of manufacturing, engineering, and design byemploying electroforming or using aluminous materials so that the lossof the transmission energy was decreased to increase the transmissionefficiency.

(3) The loss of the transmission energy was decreased by reducing thedropping angle of the escape wheel.

The above mentioned experiments however have not brought about thedesired effect of the increase on the transmission efliciency of theescapement.

On the other hand, the purpose of the present invention is to provideextremely high accuracy to a time piece by maintaining the relationshipbetween the impulse face of the escape wheel tooth and that of thepallet jewel so as to obtain a high efliciency of the escapement.

By maintaining the relations l.0 L /L O.85 and l.0 L /L 0.85, where L isthe length of the impulse face of the escape wheel tooth, L is thelength of the impulse face of the entry pallet jewel of the anchor, andL is the length of the impulse face of the exit pallet jewel of theanchor, the transmission efiiciency of the escapement can be greatlyimproved.

The high transmission efficiency of the whole escapement can be obtainedby improving the efficiency of the entry pallet and the exit palletseparately. In other words, if either of the above-mentioned relationsis satisfied, the efficiency can also be improved to some extent. But itis preferable to design an escapement so as to satisfy both relationsabove.

Of course the conventional experiments, mentioned heretofore, toincrease the transmission efficiency, can also be applied to the presentinvention to further increase the efiiciency.

The present invention will be disclosed hereinafter theoretically in theaccompanying drawings.

Referring to FIG. 2, the escape wheel portion which rotates on an axisof O in the direction of the arrow rotates the anchor portion on an axisof 0 by the force F passing through the point of contact C. F representsthe force without friction. on represents a friction angle. P and P isthe length of a perpendicular line drawn on the extension line of theforce F from O and 0 respectively. P and P is also the length of aperpendicular line drawn on the extension line of the force F. A and Brepresent the distance between 0, and C, or between O and C,respectively. L represents the length between 0- and 0 a is CO O 0 is OCO and [3 is (18OCO O A is an angle formed with a segment of a line 0 Cand F. and represent angles in polar coordinates where 0 and 0 are theorigin thereof correspondingly.

Generally from FIG. 2, the transmission efiiciency 1; is given by thefollowing equation:

And assuming that torque of the escape wheel portion is M, we can write:

FP '=M Since the emitting energy of the escape Wheel side is equal tothe absorbing energy of the anchor side under no friction, the followingequation can be obtained:

Assuming that the amount of M is constant, the Equation 1 and 2 lead to:

Further from the equations 3 and 4,

I I f 1 2 /f 5) In FIG. 2, we can read P =A sin (1r0)\) (6) P =B sin (7)P '=A sin (1r0)\+0c) (8) P '=B sin ()\a) (9) FIG. 3 shows the operatingrelationship in which the impulse face of the entry pallet jewel islifted by the locking corner 17 of the escape wheel tooth. The marksemployed in FIG. 3 mean the same as those in FIG. 2.

R is the length between 0 and the locking corner 17 of the escape wheeltooth. R is the length between 0 and the leaving corner 18 of the escapewheel tooth. Act is an angle formed with the segments of lines R and R Sis the length between 0 and the locking corner 19 of the anchor. S isthe length between 0 and the leaving corner 20 of the anchor. Afr is anangle formed with the segments of lines S and S Now in order to obtainthe transmission efficiency of a clubtooth lever escapement under thecondition shown in "FIG. 3, the following equations are substituted intothe Equation 6, 7, 8 and 9. Namely,

A 6+ cos- R R sin Aa /L +S +2LS cos B R1 +Rg +2R1Rg cos Au. fi 2+ flThus the total static transmission efliciency of the entry pallet sidecan be obtained with consideration for the transmission efiiciency dueto impulse above-mentioned and the losses due to disengagement anddropping of the escapement.

FIG. 5 shows the operating relationship in which the escape wheel toothis impelled against the exit pallet jewel. As is apparent from FIG. 5,the total transmission efliciency 1 of the exit pallet side can becalculated in approximately the same manner as calculated in the case ofthe entry pallet side, by employing the following Therefore thetransmission efficiency 1 between the escape wheel and the anchor isgiven:

where is the rotating angle of the escape wheel while the entry palletside is operated. is that of the exit pallet side.

It was found from the calculation by the computer that the extremelyhigh transmission efiicienoy could be obtained when satisfying thefollowing relations:

L 1 0.85 (12) L /L 20.85 (13) where L /R +R 2R R cos AOL is the impulseface length of the escape wheel tooth (length between 17 and 18 in FIG.3);

L /S +S -2S S cos A13 is the impulse face length of the entry palletjewel (length between 19 and 20 in FIG. 3); and

L /S +S 2S S cos A 6 is the impulse face length of the exit palletjewel.

S S and AB (not shown) of the exit pallet jewel correspond to S S and ABof the entry pallet jewel respectively.

If L /L ZLO, L /L l.0, the Width of the pallet jewel must be made smallor with the conventional pallet jewel the width of the escape Wheeltooth must be made fairly large. Therefore if the conventional escapewheel and the anchor are employed with only a slight change it requiresthe following ratios i.e. L /L and L /L less than 1.0 respectively. Evenif the width is less than 1.0 the transmission efiiciency can beincreased more than 20 to 30% compared with that of the conventionalescapement. It is also economical since great change in design orstructure is not required for the conventional watch parts.

Minimization of the pallet jewel in width makes it difiicult to cut orpolish rubies which are used as the materials for pallet jewels.

In the conventional clubtooth escapement, the following relations can begiven:

and

Namely, in the conventional escapement, the length of the impulse faceof the escape wheel tooth is fairly shorter than that of the anchor.

As can be understood from the above description, the relations among L Land L have not been considered in the improvement of the efliciency ofthe conventional escapement. In other words, the relation among L L andL shown above have been employed only customarily in the conventionalescapement and they have been decided regardless of the improvement ofthe eificiency of the escapement.

On the other hand, in the present invention, the improvement of theescapement efiiciency can be performed by keeping the relations among LL and L satisfactorily.

The results of the experiment where the escapement according to thepresent invention is compared with the conventional one will bedisclosed hereinafter only by the examples.

In this case, the conventional escapement has L /L -0.5 and L /L -0.5,while the escapement according to the invention has L /L -0.9 and L /L-0.9.

Two kinds of wrist watches with the above-mentioned escapements, whichshow the moment of inertia of 910 mg. mm. and 36,000 vibrations/hourrespectively, were compared with each other in the amplitude in thehorizontal position.

The results are as follows:

FIG. 6 shows the relationship between the amplitude and the torque inthe horizontal and vertical position in the conventional escapement andthe escapement according to the invention.

As a result, the ratio of the mainspring torque to the same amplitude of210 between the conventional escapement having the torque of 120 gem.and the escapement having the torque of 100 gcrn. according to theinvention is 120/ 100:1.2. Thatis, the transmission efiiciency in theescapement according to the invention can be increased by 20%.

Further, since the transmission efiiciency of the train wheels isgenerally 70% and Q value of the balance is approximately 300, thetransmission efliciency of the escapement can be calculated from TableI. Namely, the transmission efliciency of the conventional escapement is31%, while that of the escapement according to the invention is 37%. Inother words, the transmission efliciency of the escapement according tothe invention can be increased by about 1.2 times as that of theconventional escapement.

FIG. 7 shows the transmission efficiency of the timepieces having thedifferent frequency. As can be seen from FIG. 7, the transmissionefficiency of the escapement according to the invention is far higherthan that of the conventional escapement, making it possible to decreasethe isochronism error caused by a hairspring, positional error andescapement error and thus insuring the production of timepieces withextremely high frequency.

What is claimed is:

1. A clubtooth lever escapement with high transmission efficiencycomprising an escape wheel having a plurality of teeth, each of saidteeth having an impulse face; and an anchor having an entry pallet jeweland an exit pallet jewel, each of said entry and exit pallet jewelsbeing formed with an impulse face for cooperative engagement with saidescape wheel teeth for the transmission of energy from said escape wheelto said anchor, and wherein 1.0 L /L 20.85, where L is the length of theimpulse face of the escape wheel teeth, and L is the length of theimpulse face of the entry pallet jewel of the anchor.

2. A clubtooth lever escapement as recited in claim 1, wherein 1.0 L /Lz0.85, where L is the length of the impulse face of the exit palletjewel of the anchor.

3. A clubtooth lever escapement with high transmission efliciencycomprising an escape wheel having a plurality of teeth, each of saidteeth having an impulse face; and an anchor having an entry pallet jeweland an exit pallet jewel, each of said entry and exit pallet jewelsbeing formed with an impulse face for cooperative engagement with saidescape wheel teeth for the transmission of energy from said escape wheelto said anchor, and wherein 1.0 L /L 20.85, where L is the length of theimpulse face of the escape wheel teeth and L is the length of theimpulse face of the exit pallet jewel of the anchor.

References Cited UNITED STATES PATENTS 856,091 6/1907 Ohlson 58-1161,044,054 11/ 1912 Jeanmairet 58-116 1,928,554 9/1933 Beehler 58-1162,444,178 6/1948 Weinberger 5 8-116 X 3,425,212 2/1969 Verde 58-116FOREIGN PATENTS 1,096,039 12/ 1967 Great Britain 58-116 342,897 1/1960'Switzerland 58-116 RICHARD B. WILKINSON, Primary Examiner S. A. WAL,Assistant Examiner

